Nippon Telegraph and Telephone Corp. and Asics Corp. have developed a prototype shirt with a sensor that can warn the wearer when the risk of heatstroke is heightened.

The companies plan to bring the trial product to practical use by summer 2020 after further experiments.

A sensor embedded on the back of the shirt measures the intensity of sunlight, temperature and humidity next to the skin, as well as the wearer’s heart rate and other relevant data. The information can be read on the user’s smartphone.

The companies envisage additional functions, such as an alarm that sounds when the heatstroke risk is great and a warning to tell the wearer to take a rest and receive hydration.

They also plan to give the garment the ability to adopt various yardsticks to evaluate heatstroke risks based on the age of the wearer.

Japan is coming off a summer that set a number of record-high temperatures.

The shirt is aimed at people who work outdoors, athletes and elderly people who are at danger of suffering from heatstroke even if they stay indoors.